Film

ABSTRACT

The present invention provides a wrap film or shrink film formed from a resin composition containing [I] a propylene polymer in an amount of 1 to 99 mass %, and [II] an olefin-based polymer in an amount of 99 to 1 mass %, wherein [I] the propylene polymer satisfies the following requirements of: (1) a meso pentad fraction (mmmm) is 0.2 to 0.6, and (2) a racemic pentad fraction (rrrr) and (1−mmmm) satisfy the following relation: [rrrr/(1−mmmm)]≦0.1. The wrap film or shrink film exhibits excellent characteristics, and does not generate a toxic gas derived from chlorine, such as hydrogen chloride gas or dioxin, when being incinerated.

TECHNICAL FIELD

The present invention relates to films, in details, a wrap film forcommercial or household use, and to a shrink film employed for packagingand other purposes. More particularly, the invention relates to a wrapfilm which contains no chlorine, which is environmentally friendly,which exhibits excellent safety, and which exhibits characteristicsrequired of wrap film, such as wrapping-ability, transparency, andrestoration from deformation; and to a shrink film which contains nochlorine, which is environmentally friendly, which exhibits excellentsafety, transparency, glossiness, and low-temperature shrink-packagingcharacteristics, and which enables packaging of a product havingrelatively low strength while providing the product with goodappearance, without involving deformation of the product.

BACKGROUND ART

Conventionally, vegetables and fruits, meats, fishes, processed foodsmade from these, and cooked foods such as delicatessen items—which aresold in department stores, supermarkets, and grocery stores—have beenplaced on lightweight trays formed from foaming resin, and wrapped withfilm. In the home, when a grocery item is stored in a freezer or arefrigerator, or heated in a microwave oven, the item is placed in acontainer and wrapped with film.

Such wrapping film is required to exhibit excellent characteristics interms of, for example, transparency, finishing appearance, wrappingefficiency, resistance to poking, and restoration from deformation whenbeing pushed with a finger. In general, a polyvinyl-chloride-based resinsuch as polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC) iswidely employed for producing a film satisfactorily exhibiting suchwrapping characteristics.

However, since a polyvinyl-chloride-based resin such as polyvinylchloride (PVC) or polyvinylidene chloride (PVDC) contains chlorine inthe molecule, when a film formed from such a resin is incinerated afterbeing used and disposed of, a toxic substance such as hydrogen chloridegas or dioxin is generated, thereby raising environmental problems.Further, elution of a plasticizer, which is incorporated into a wrapfilm in large amount for softening the film, is problematic from theviewpoint of safety.

In order to solve such problems, attempts to employ a polyethylene filmor a polypropylene film have been made, and such a film has been putinto practice. Although a polyethylene film exhibits goodlow-temperature characteristics, it exhibits poor heat resistance,whereas a polypropylene film exhibits poor low-temperaturecharacteristics and high heat resistance. In addition, a polyethylenefilm or a polypropylene film exhibits unsatisfactory adhesion to, forexample, a tray, and adhesion between polyethylene films or betweenpolypropylene films is unsatisfactory.

Therefore, there have been proposed various techniques forincorporating, into a propylene-based resin, ethylene-propylene rubber,a styrene-ethylene-butylene-styrene block copolymer, modifiedpolyolefin, polybutene, a hydrocarbon resin, an adhesion-imparting aid,etc. However, such an additive does not necessarily exhibit sufficientmiscibility with a polypropylene-based resin, and raises problemsincluding roughing of a surface, lowering of transparency, lowering offilm forming-ability, and bleeding of a low molecular weight compoundserving as an adhesion-imparting aid.

Japanese Patent Application Laid-Open (kokai) No. 11-29667 discloses awrap film formed from a resin composition containing (A) (50 to 98 partsby weight) of a polypropylene-based resin and (B) (2 to 50 parts byweight) of an ethylene-α-olefin copolymer having a density of 0.900g/cm³ or less; and Japanese Patent Application Laid-Open (kokai) No.11-29668 discloses a wrap film formed from a resin compositioncontaining (A) (100 parts by weight) of a polypropylene-based resin and(B) (1 to 15 parts by weight)of oil and fat. However, like the cases ofthe aforementioned conventional techniques, a low-molecular-weightcompound such as polybutene or oil and fat must be incorporated intosuch a wrap film in order to secure adhesion of the wrap film.

Japanese Patent Application Laid-Open (kokai) 2000-44742 discloses awrap film containing a soft polypropylene-based resin containing (A) 20to 60 wt. % of a polypropylene having an isotactic index of at least 80;and (B) 40 to 80 wt. % of a copolymer component consisting of (I) 25 to95 wt. % of a crystalline component which is a copolymer component ofethylene and an olefin having at least four carbon atoms, contains 50 to95 wt. % of ethylene and has crystalline polyethylene which is insolublein xylene at 25° C., and (II) 5 to 75 wt. % of an amorphous componentwhich is soluble in xylene at 25° C. When characteristics of the wrapfilm are evaluated, instead of a single-layer film consisting of thewrap film, a multi-layer film including the wrap film and outer layersformed from a propylene-ethylene-butene-1 copolymer and anethylene-vinyl acetate copolymer is employed. Therefore, characteristicsof the polypropylene-based resin are not reflected in characteristics ofthe multi-layer film. Furthermore, transparency of the wrap film is notsatisfactory.

Although a wrap film formed from a polyolefin-based resin containing nochlorine can solve environmental problems, characteristics of the wrapfilm are inferior to those of a wrap film formed from apolyvinyl-chloride-based resin. Therefore, in actuality, wrap filmsformed from a polyvinyl-chloride-based resin are widely used.

Heat shrink packaging employing a heat-shrinkable film (shrink film)—inwhich an object is wrapped with a shrink film, and the object is causedto pass through a heating furnace so as to shrink the film, whereby thefilm adheres to the object; or a plurality of objects are bound togetherwith a shrink film—is widely carried out for packaging of cup noodleproducts or for lamination packaging of, for example, notebooks ortissue paper.

At present, a stretched film formed from, for example, apolyvinyl-chloride-based resin such as polyvinyl chloride (PVC) orpolyvinylidene chloride (PVDC), a polyethylene-based resin, or apolypropylene resin is employed as a shrink film in heat shrinkpackaging. A shrink film is required to exhibit excellentcharacteristics in terms of, for example, heat shrinking-ability duringpackaging, melting-breakage resistance, side welding property, hot slipproperty, transparency after packaging, high glossiness, mechanicalstrength, and appearance after packaging (i.e., the edge of the filmadheres to an object without forming wrinkles). Generally, a shrink filmformed from a polyvinyl-chloride-based resin, which satisfactorilyexhibits such characteristics, is employed.

However, since a polyvinyl-chloride-based resin such as polyvinylchloride (PVC) or polyvinylidene chloride (PVDC) contains chlorine inthe molecule, when a film formed from such a resin is incinerated afterbeing used and disposed of, a toxic substance derived from chlorine,such as hydrogen chloride gas or dioxin, generates, thereby raisingenvironmental problems. Furthermore, elution of a plasticizer, which isincorporated into a shrink film in large amount for softening the film,is problematic from the viewpoint of safety. In addition, when a shrinkfilm formed from a polyvinyl-chloride-based resin is heated during heatshrink packaging, the resin issues a foul odor. Therefore, from theenvironmental viewpoint during packaging, demand has arisen for furtherimprovements to such a shrink film.

In order to solve such problems, attempts to employ a polyethylene filmor a polypropylene film have been made, and such a film have been putinto practice. Although a polyethylene film exhibits goodlow-temperature characteristics, it exhibits poor heat resistance andmelting-breakage resistance, whereas a polypropylene film exhibits poorlow-temperature characteristics and high heat resistance. When heatingtemperature is increased during shrink packaging of a product by use ofsuch a film, the packaged product is deformed due to heat shrinkagestress, and the resultant product exhibits poor appearance, whereby thevalue of the product is lowered. Since a polyethylene film or apolypropylene film is inferior to a film formed from apolyvinyl-chloride-based resin in terms of, for example, transparencyand glossiness, a limitation is imposed on the applications of apolyethylene film or a polypropylene film.

In view of the foregoing problems, various improvements to a shrink filmformed from a polypropylene-based resin have been proposed. For example,(i) Japanese Patent Application Laid-Open (kokai) No. 7-304882 disclosesa polyolefin-based resin stretched shrink film exhibiting specificphysical properties and containing 0.01 to 5 wt. % of a polybutenecomponent, 1 to 70 wt. % of a polypropylene component, and 25 to 98.99wt. % of a propylene-ethylene random copolymer component, in which thepropylene-ethylene random copolymer component is composed of a randomcopolymer containing 10 to 40 mol % of an ethylene monomer unit and 90to 60 mol % of a propylene monomer unit.

(ii) Japanese Patent Application Laid-Open (kokai) No. 9-176335discloses a shrinkable film predominantly comprising crystallinepolypropylene wherein a peak temperature of an elution curve measured bya temperature rising elution fractionation method usingo-dichlorobenzene serving as a solvent is 90 to 110° C. and an elutingintegrated weight fraction is 0 to 10 wt. % at 20° C. or lower, 60 to 80wt. % at temperature range within 20 to 100° C., and 10 to 40 wt. % attemperature range within 100 to 130° C. as calculated from the elutioncurve. Specifically, the crystalline polypropylene is formed of a blockcopolymer containing 1 to 70 mass % of (a) a polypropylene component ora propylene-based random copolymer containing a propylene monomer unitin an amount of more than 90 mol %, and 30 to 99 mass % of (b) a randomcopolymer containing an ethylene monomer unit in an amount of 10 to 40mol %.

(iii) Japanese Patent Application Laid-Open (kokai) No. 10-152531discloses a stretched film formed from a propylene-ethylene randomcopolymer in which the ethylene unit content of the copolymer, the meltindex, the boiled diethyl ether extraction amount, and the melting pointsatisfy specific relations, and the isotactic triad fraction is at least98 mol %.

Each of the aforementioned polypropylene resin films predominantlycontains a copolymer of propylene and another α-olefin, and is improvedin the point that stretching temperature; i.e., heating temperatureduring shrink packaging, can be reduced. However, as is clear from theExamples described in these publications, transparency and glossiness ofthese films are not satisfactory. Therefore, the value of a productpackaged with any of these films is lower than that of the productpackaged with a conventionally employed polyvinyl-chloride-based resinfilm.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a wrap film whichexhibits characteristics required for wrap film, such aswrapping-ability, transparency, restoration from deformation, and pokingresistance, which contains no chlorine, which, when being incinerated,does not generate a toxic substance derived from chlorine, such ashydrogen chloride or dioxin, and which is environmentally friendly.

Another object of the present invention is to provide a shrink filmformed from an olefin-based resin, which exhibits excellent heatshrinking-ability required of shrink film, which is shrinkable at lowtemperature, which is improved as compared with a conventionalpolypropylene-based resin film in terms of, for example, transparencyand glossiness, which exhibits characteristics comparable to those of apolyvinyl-chloride-based resin film, which contains no chlorine, which,when being incinerated, does not generate a toxic substance such ashydrogen chloride or dioxin, and which is environmentally friendly.

As a result of extensive investigations for attaining the aforementionedobjects, the present inventors have found that providing a film formedfrom a composition containing a specific propylene polymer and anolefin-based polymer can attain the objects. The present invention hasbeen accomplished on the basis of this finding. Accordingly, the presentinvention provides the following films.

[1] A wrap film formed from a resin composition comprising

[I] a propylene polymer in an amount of 1 to 99 mass %, and

[II] an olefin-based polymer in an amount of 99 to 1 mass %, wherein [I]the propylene polymer satisfies the following requirement of:

(1) a meso pentad fraction (mmmm) is 0.2 to 0.6, and

(2) a racemic pentad fraction (rrrr) and (1−mmmm) satisfy the followingrelation:

[rrrr/(1−mmmm)]≦0.1.

[2] The wrap film as defined in the item [1], wherein [I] the propylenepolymer satisfies the following requirement of:

(3) an intrinsic viscosity [η] measured at 135° C. in tetralin is 1 to 3deciliter/g.

[3] The wrap film as defined in the item [1] or the item [2], wherein[I] the propylene polymer satisfies the following requirement of:

(4) an amount of a component which is eluted at 25° C. or lower throughtemperature rise chromatography (W25) is 20 to 100 mass %.

[4] The wrap film as defined in any one of the items [1] to [3], wherein[I] the propylene polymer is polymerized by the use of a metallocenecatalyst containing a promoter and a transition metallic compound inwhich a cross-linking structure is formed via two cross-linking groups.

[5] The wrap film as defined in any one of the items [1] to [4], wherein[II] the olefin-based polymer is a propylene-based polymer.

[6] A multi-layer wrap film comprising at least one layer formed from aresin composition as recited in any one of the items [1] to [5].

As a result of extensive investigations for attaining the aforementionedobjects, the present inventors have also found that the objects can beattained by providing a stretched film produced through stretching of afilm formed from a resin composition containing a specific propylenepolymer and an olefin-based polymer. The present invention has beenaccomplished on the basis of this finding. Accordingly, the presentinvention provides the following films.

[7] A stretched shrink film formed from a resin composition comprising[I] a propylene polymer in an amount of 1 to 99 mass %, and [II] anolefin-based polymer in an amount of 99 to 1 mass %, wherein [I] thepropylene polymer satisfies the following requirements of:

(1) a meso pentad fraction (mmmm) is 0.2 to 0.6, and

(2) a racemic pentad fraction (rrrr) and (1−mmmm) satisfy the followingrelation:

[rrrr/(1−mmmm)]≦0.1.

[8] The shrink film as defined in the item [7], wherein [I] thepropylene polymer satisfies the following requirement of:

(3) an intrinsic viscosity [η] measured at 135° C. in tetralin is 1 to 3deciliter/g.

[9] The shrink film as defined in the item [7] or item [8], wherein [I]the propylene polymer satisfies the following requirement of:

(4) an amount of a component which is eluted at 25° C. or lower throughtemperature rise chromatography (W25) is 20 to 100 mass %.

[10] The shrink film as defined in any one of the items [7] to [9],wherein [I] the propylene polymer is polymerized by the use of ametallocene catalyst containing a promoter and a transition metalliccompound in which a cross-linking structure is formed via of twocross-linking groups.

[11] The shrink film as defined in any one of the items [7] to [10],wherein [II] the olefin-based polymer is a propylene-based polymer.

[12] A multi-layer shrink film comprising at least one layer formed froma resin composition as recited in any one of the items [7] to [11].

BEST MODE FOR CARRYING OUT THE INVENTION

The wrap film or shrink film of the present invention is formed from aresin composition containing [I] a specific propylene polymer in anamount of 99 to 1 mass % and [II] an olefin-based polymer in an amountof 1 to 99 mass %. That is, the wrap film or shrink film of the presentinvention is formed from a resin composition containing the specificpropylene polymer as an essential component. The wrap film and shrinkfilm of the present invention will next be described in detail.

The [I] specific propylene polymer employed for forming the wrap film orshrink film of the present invention satisfies the followingrequirements of:

(1) a meso pentad fraction (mmmm) is 0.2 to 0.6, and

(2) a racemic pentad fraction (rrrr) and (1−mmmm) satisfy the followingrelation:

[rrrr/(1−mmmm)]≦0.1.

In [I] the propylene polymer employed in the present invention,preferably, the meso pentad fraction (mmmm) is 0.3 to 0.5. The ratio ofthe racemic pentad fraction (rrrr) to (1−mmmm); i.e., [rrrr/(1−mmmm)],is preferably 0.08 or less, more preferably 0.06 or less, much morepreferably 0.05 or less.

When (1) the meso pentad fraction (mmmm) of [I] the propylene polymerexceeds 0.6, and (2) the racemic pentad fraction (rrrr) and (1−mmmm)fails to satisfy the above-described relation, a film formed from theresin composition may fail to secure characteristics required for wrapfilm, such as wrapping-ability, flexibility, transparency, restorationfrom deformation, and resistance to poking. When (1) the meso pentadfraction (mmmm) is less than 0.2, since film formation stability islowered, problems occur due to bleeding of an additive, and strength islowered, rendering the resultant film unsuitable as a wrap film.

In the case where (1) the meso pentad fraction (mmmm) of [I] thepropylene polymer exceeds 0.6, and (2) the racemic pentad fraction(rrrr) and (1−mmmm) fails to satisfy the above-described relation, whena product is packaged with a shrink film formed from the resincomposition, the packaged product tends to be deformed due to heatshrinkage of the shrink film. Therefore, the product which has undergoneheat shrink packaging exhibits poor appearance, and the product may bebroken. When (1) the meso pentad fraction (mmmm) is less than 0.2, sincefilm formation stability is lowered, problems occur due to bleeding ofan additive, and strength is lowered, rendering the resultant filmunsuitable as a shrink film.

The meso pentad fraction (mmmm) which specifies [I] the propylenepolymer employed in the present invention is obtained by means of amethod proposed in “Macromolecules, 6, 925 (1973)” by A. Zambelli, etal., and is defined as the meso fraction of a pentad unit of apolypropylene molecular chain measured on the basis of the signalattributed to the methyl group of the propylene polymer in the ¹³C-NMRspectrum. The greater the meso pentad fraction, the higher thestereoregularity of the propylene polymer. When the meso pentad fraction(mmmm) of the propylene polymer is less than 0.2, formation of a filmmay be difficult, due to stickiness of the film. In contrast, when themeso pentad fraction (mmmm) exceeds 0.6, due to lowering of flexibilityand adhesion, wrapping-ability of the resultant film may becomeunsatisfactory.

The racemic pentad fraction (rrrr) which specifies the propylene polymeremployed in the present invention is the racemic fraction of a pentadunit of a polypropylene molecular chain. The value [rrrr/(1−mmmm)] isobtained on the basis of the aforementioned meso fraction and racemicfraction of a pentad unit, and is employed as an index for expressinguniformity in stereoregularity distribution of the propylene polymer.The greater the value [rrrr/(1−mmmm)], the higher the stereoregularityof the propylene polymer. When the value [rrrr/(1−mmmm)] is large, likethe case where conventional polypropylene is produced through the use ofa conventional catalyst, a mixture of high-stereoregular polypropylene(PP) and amorphous polypropylene (APP) is produced. As a result, filmforming-ability is lowered due to high stickiness of the mixture, andthe resultant film exhibits poor transparency. When the value[rrrr/(1−mmmm)] of [I] the propylene polymer exceeds 0.1, the resultantfilm becomes sticky.

The ¹³C-NMR spectrum of the propylene polymer is measured by means ofpeak attribution proposed in “Macromolecules, 8, 687 (1975)” by A.Zambelli, et al., and measured by the use of the following apparatusunder the following conditions.

Apparatus: JNM-EX400-Model ¹³C-NMR spectrometer (produced by JEOL Ltd.)

Method: Complete proton decoupling method

Concentration: 220 mg/milliliter

Solvent: A mixed solvent of 1,2,4-trichlorobenzene and bi-benzene (withmass ratio of 90:10)

Temperature: 130° C.

Pulse width: 45°

Pulse interval: 4 seconds

Integration: 10,000 times

Preferably, [I] the specific propylene polymer employed in the presentinvention satisfies, in addition to the aforementioned requirements, thefollowing requirement:

(3) an intrinsic viscosity [η] measured at 135° C. in tetralin is 1 to 3deciliter/g. In the case where a wrap film is formed, the intrinsicviscosity [η] affects forming-ability of the film. When T-die castingmolding is performed, the intrinsic viscosity [η] is more preferably 1.0to 2.5 deciliter/g. When inflation molding is performed, the intrinsicviscosity [η] is more preferably 1.5 to 3.0 deciliter/g. In the casewhere a shrink film is formed, the intrinsic viscosity [η] affectsforming-ability and stretching-ability of the film. When tenter biaxialstretching or tubular biaxial stretching is performed, the intrinsicviscosity [η] is more preferably 1.5 to 3.0 deciliter/g. When theintrinsic viscosity [η] is less than 1 deciliter/g, film forming-abilityis lowered, whereas when the intrinsic viscosity [η] exceeds 3deciliter/g, melting viscosity becomes high, fluidity is lowered, andfilm forming-ability is lowered.

Preferably, [I] the propylene polymer satisfies, in addition to theaforementioned requirement (1), (2), and (3), the following requirementof:

(4) an amount of a component which is eluted at 25° C. or lower throughtemperature rise chromatography (W25) is 20 to 100 mass %. Morepreferably, W25 is 50 to 100 mass %. The term “W25” is defined as theamount of an eluted component (mass %) which is not adsorbed onto afiller contained in a TREF column (column temperature: 25° C.), and W25is obtained on the basis of an elution curve prepared throughtemperature rise chromatography performed by means of the apparatus andoperation method and under the measurement conditions which aredescribed below in Examples. W25 is an index for expressing whether ornot the propylene polymer is soft. When W25 is large, the amount of acomponent of low elastic modulus is increased, and/or uniformity ofstereoregularity distribution fails to be attained satisfactorily. Inthe present invention, when W25 is less than 20%, the propylene polymerfails to exhibit, for example, flexibility.

Preferably, [I] the specific propylene polymer employed in the presentinvention also satisfies the following requirements.

(i) A molecular weight distribution (Mw/Mn) as measured through gelpermeation chromatography (GPC) is preferably 4 or less, more preferably3.5 or less. When the molecular weight distribution (Mw/Mn) exceeds 4,film forming-ability may be lowered. The molecular weight distribution(Mw/Mn) is obtained by means of gel permeation chromatography (GPC) asdescribed below in Examples.

(ii) A melting endothermic amount (ΔH) obtained by a differentialscanning calorimeter (DSC) measurement of the polymer is preferably 30J/g or less. The value AH is an index for expressing whether or not thepropylene polymer is soft. When the value AH grows large, it means thatthe elastic modulus of the propylene polymer is high, and the softnessof the polymer reduces.

(iii) The propylene polymer may have a melting point (Tm). From theviewpoint of softness of the polymer, preferably, the polymer has nomelting point or a melting point (Tm) as low as 100° C. or less. Thevalues of ΔH and Tm are obtained by means of the DSC measurement methoddescribed below in Examples.

No particular limitation is imposed on [I] the propylene polymeremployed in the present invention, so long as the polymer satisfies theaforementioned specific requirement (1) and (2). The propylene polymermay be copolymerized with a comonomer (2 mass % or less) other thanpropylene. Examples of the comonomer include ethylene, 1-butene,1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene,1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. The propylenepolymer may be a copolymer obtained through copolymerization ofpropylene with one or more of these comonomers.

No particular limitation is imposed on the production method for [I] thepropylene polymer employed in the present invention, so long as thepolymer satisfies the aforementioned requirement (1) and (2).Preferably, the propylene polymer is produced through, for example, aknown method (see WO99/67303) in which propylene is subjected topolymerization or copolymerization by the use of a metallocene catalystcontaining (A) a transition metallic compound in which a cross-linkingstructure is formed via two cross-linking groups and (B) a promoter.Specifically, the propylene polymer is produced through a method inwhich polymerization of propylene or copolymerization of propylene witha small amount of another α-olefin is performed in the presence of apolymerization catalyst containing (A) a transition metallic compoundand (B) a promoter component selected from among (B-1) a compoundcapable of forming an ionic complex through reaction with (A) thetransition metallic compound or a derivative thereof and (B-2) analuminoxane, (A) the transition metallic compound being represented bythe following formula (I):

wherein M represents a metal selected from among elements belonging togroups 3 through 10 in the periodic table or elements belonging to thelanthanide series; each of E¹ and E², which may be identical with ordifferent from each other, represents a ligand selected from among asubstituted cyclopentadienyl group, an indenyl group, a substitutedindenyl group, a heterocyclopentadienyl group, a substitutedheterocyclopentadienyl group, an amido group, a phosphide group, ahydrocarbon group, and a silicon-containing group, E¹ and E² form across-linking structure via A¹ and A²; X represents a σ-bonding ligand(or σ-bonding ligands), and if a plurality of ligands are represented byX, the ligands may be identical or differ from one another, and a ligandrepresented by X may be cross-linked with another ligand represented byX, a ligand represented by E¹, a ligand represented by E², or a Lewisbase represented by Y; Y represents a Lewis base (or Lewis bases), andif a plurality of bases are represented by Y, the bases may be identicalor differ from one another, and a base represented by Y may becross-linked with another base represented by Y, a ligand represented byE¹, a ligand represented by E², or a ligand represented by X; each of A¹and A², which may be identical with or different from each other, is adivalent cross-linking group capable of bonding two ligands, andrepresents a hydrocarbon group having 1 to 20 carbon atoms, ahalogen-containing hydrocarbon group having 1 to 20 carbon atoms, asilicon-containing group, a germanium-containing group, a tin-containinggroup, —O—, —CO—, —S—, —SO2—, —Se—, —NR¹—, —PR¹—, —P(O)R¹—, —BR¹—, or—AlR¹— (wherein R¹ represents a hydrogen atom, a halogen atom, ahydrocarbon group having 1 to 20 carbon atoms, or a halogen-containinghydrocarbon group having 1 to 20 carbon atoms); q represents an integerof 1 through 5 and [(the valence of M) −2]; and r represents an integerof 0 through 3.

Specific examples of the transition-metallic compound represented by theformula (I) include(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(3-n-butylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(3-trimethylsilylmethylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(3-phenylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(4,5-benzoindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(4-isopropylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(5,6-dimethylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(4,7-di-i-propylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(4-phenylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(3-methyl-4-i-propylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)bis(5,6-benzoindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-isopropylidene)-bis(indenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-isopropylidene)-bis(3-methylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-isopropylidene)-bis(3-i-propylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-isopropylidene)-bis(3-n-butylindenyl)zirconiumdichloride;(1,2′-dimethylsilylene)(2,1′-isopropylidene)-bis(3-trimethylsilylmethylindenyl)zirconiumdichloride; and compounds obtained by substituting titanium or hafniumfor zirconium constituting the aforementioned compounds.

Examples of (B-1) the compound capable of forming an ionic complexthrough reaction with (A) the transition metallic compound or aderivative thereof include triethylammonium tetraphenylborate,tri-n-butylammonium tetraphenylborate, trimethylammoniumtetraphenylborate, tetraethylammonium tetraphenylborate,methyl(tri-n-butyl)ammonium tetraphenylborate, andbenzyl(tri-n-butyl)ammonium tetraphenylborate. These (B-1) compounds maybe employed singly or in combination of two or more species.

Examples of (B-2) the aluminoxane include methyl aluminoxane, ethylaluminoxane, and isobutyl aluminoxane. These aluminoxanes may beemployed singly or in combination of two or more species.

The aforementioned polymerization catalyst may contain, in addition tothe aforementioned components (A) and (B), an organic aluminum compoundserving as a component (C). Examples of the organic aluminum compoundserving as the component (C) include trimethylaluminum,triethylaluminum, triisopropylaluminum, triisobutylaluminum,dimethylaluminum chloride, diethylaluminum chloride, methylaluminumdichloride, ethylaluminum dichloride, dimethylaluminum fluoride,diisobutylaluminum hydride, diethylaluminum hydride, and ethylaluminumsesquichloride. These organic aluminum compounds may be employed singlyor in combination of two or more species.

When polymerization of propylene is carried out, at least one componentof the aforementioned catalyst may be supported on an appropriatecarrier. No particular limitation is imposed on the type of the carrier,and an inorganic oxide carrier, an inorganic carrier other than aninorganic oxide carrier, or an organic carrier may be employed.Particularly, an inorganic oxide carrier or an inorganic carrier otherthan an inorganic oxide carrier is preferred.

No particular limitation is imposed on the polymerization method, andany known method such as a slurry polymerization method, a vapor-phasepolymerization method, a bulk polymerization method, a solutionpolymerization method, or a suspension polymerization method may beemployed. Of these, a bulk polymerization method and a solutionpolymerization method are preferred.

Regarding polymerization conditions, the polymerization temperature istypically −100 to 250° C., preferably −50 to 200° C., more preferably 0to 130° C. The ratio of raw material to catalyst; i.e., the ratio by molof the raw material monomer/the aforementioned component (A), ispreferably 1 to 10⁸, more preferably 100 to 10⁵ The polymerization timeis typically five minutes to 10 hours. The reaction pressure istypically ambient pressure to 20 MPa (gauge), preferably ambientpressure to 10 MPa (gauge).

Next will be described the other component of the resin composition forforming the wrap film or shrink film of the present invention. Examplesof the other component (i.e., [II] the olefin-based polymer) includepolypropylene, a propylene-α-olefin copolymer, apropylene-ethylene-diene copolymer, high-pressure-processed low-densitypolyethylene, high-density polyethylene, an ethylene-α-olefin copolymerhaving a density of 850 to 940 kg/m³, an ethylene-vinyl acetatecopolymer, and a hydrogenated styrene-based elastomer. Of these,polypropylene, a propylene-α-olefin copolymer, and an ethylene-α-olefincopolymer having a density of 850 to 940 kg/m³ are preferred, and apropylene-based polymer is particularly preferred. These olefin-basedpolymers may be employed in combination of two or more species.

The resin composition for forming the wrap film or shrink film of thepresent invention contains [I] the propylene polymer in an amount of 1to 99 mass % and [II] the olefin-based polymer in an amount of 99 to 1mass %. In the case where a wrap film is formed, preferably, thecomposition containing [I] the propylene polymer in an amount of 25 to96 mass % and [II] the olefin-based polymer in an amount of 75 to 4 mass% is employed. More preferably, the composition containing [I] thepropylene polymer in an amount of 40 to 92 mass % and [II] theolefin-based polymer in an amount of 60 to 8 mass % is employed. Muchmore preferably, the composition containing [I] the propylene polymer inan amount of 50 to 90 mass % and [II] the olefin-based polymer in anamount of 50 to 10 mass % is employed.

In the case where a shrink film is formed, preferably, the compositioncontaining [I] the propylene polymer in an amount of 20 to 96 mass % and[II] the olefin-based polymer in an amount of 80 to 4 mass % isemployed. More preferably, the composition containing [I] the propylenepolymer in an amount of 30 to 94 mass % and [II] the olefin-basedpolymer in an amount of 70 to 6 mass % is employed. Much morepreferably, the composition containing [I] the propylene polymer in anamount of 40 to 92 mass % and [II] the olefin-based polymer in an amountof 60 to 8 mass % is employed.

In the case where the incorporation amount of [I] the propylene polymeris small in the resin composition, when a wrap film is formed from thecomposition, characteristics of the resultant wrap film, such asflexibility, transparency, restoration from deformation, andwrapping-ability, are deteriorated. In contrast, in the case where theincorporation amount of [I] the propylene polymer is large in the resincomposition, film formation may be disturbed, and difficulty may beencountered in consistent production of a wrap film at highproductivity. Therefore, the incorporation amount of [I] the propylenepolymer is appropriately determined in consideration of, for example,the meso pentad fraction and the intrinsic viscosity [η] of [I] thepropylene polymer, and the type, molecular weight, and melting viscosityof [II] the olefin-based polymer, particularly in consideration ofwrapping-ability.

In the case where the incorporation amount of [I] the propylene polymeris small in the resin composition, when a shrink film is formed from thecomposition, a product packaged with the shrink film tends to bedeformed or broken due to heat shrinkage of the film, andcharacteristics of the shrink film, such as packaging appearance, aredeteriorated. In contrast, in the case where the incorporation amount of[I] the propylene polymer is large in the resin composition, filmformation stability and stretching-ability are lowered, and difficultymay be encountered in consistent production of a wrap film at highproductivity. Therefore, the incorporation amount of [I] the propylenepolymer is appropriately determined in consideration of, for example,the meso pentad fraction and the intrinsic viscosity [η] of [I] thepropylene polymer, and the type, molecular weight, and melting viscosityof [II] the olefin-based polymer, particularly in consideration ofpackaging-ability, film forming-ability, and stretching-ability.

When the wrap film or shrink film of the present invention is produced,if desired, a variety of known additives may be incorporated into theresin composition.

Examples of the additive that may be incorporated into the resincomposition include an antioxidant, a neutralizing agent, a slip agent,an anti-blocking agent, an anti-fog agent, a lubricant, a nucleatingagent, and an antistatic agent. These additives may be employed singlyor in combination of two or more species. Examples of the antioxidantinclude a phosphorus-based antioxidant, a phenol-based antioxidant, anda sulfur-based antioxidant.

Specific examples of the phosphorus-based antioxidant includetris(nonylphenyl) phosphite; tris(2,4-di-t-butylphenyl) phosphite;distearylpentaerythritol diphosphite;bis(2,4-di-t-butylphenyl)pentaerythritol phosphite;bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol phosphite;2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite;tetrakis(2,4-di-t-butylphenyl)-4,4-biphenylene-di-phosphonite; Adekastab1178 (Asahi Denka Co., Ltd.); Sumilizer TNP (Sumitomo Chemical Co.,Ltd.); JP-135 (Johoku Kagaku K.K.); Adekastab 2112 (Asahi Denka Co.,Ltd.); JPP-2000 (Johoku Kagaku K.K.); Weston618 (General Electric Co.);Adekastab PEP-24G (Asahi Denka Co., Ltd.); Adekastab PEP-36 (Asahi DenkaCo., Ltd.); Adekastab HP-10 (Asahi Denka Co., Ltd.); SandstabP-EPQ(Sandoz Ltd.); and Phosphite 168 (Ciba Specialty Chemicals Corp.).

Specific examples of the phenol-based antioxidant include2,6-di-t-butyl-4-methylphenol;n-octadecyl-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl) propionate;tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane; tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate;4,4′-butylidenebis-(3-methyl-6-t-butylphenol); triethyleneglycol-bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl) propionate];3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane;Sumilizer BHT (Sumitomo Chemical Co., Ltd.); Yoshinox BHT (YoshitomiPharmaceutical Industries, Ltd.); Antage BHT (Kawaguchi ChemicalIndustry Co., Ltd.); Irganox 1076 (Ciba Specialty Chemicals Corp.);Irganox 1010 (Ciba Specialty Chemicals Corp.); Adekastab AO-60 (AsahiDenka Co., Ltd.); Sumilizer BP-101 (Sumitomo Chemical Co., Ltd.);Tominox TT (Yoshitomi Pharmaceutical Industries, Ltd.); TTHP (TorayIndustries, Inc.); Irganox 3114 (Ciba Specialty Chemicals Corp.);Adekastab AO-20 (Asahi Denka Co., Ltd.); Adekastab AO-40 (Asahi DenkaCo., Ltd.); Sumilizer BBM-S (Sumitomo Chemical Co., Ltd.); Yoshinox BB(Yoshitomi Pharmaceutical Industries, Ltd.); Antage W-300 (KawaguchiChemical Industry Co., Ltd.); Irganox 245 (Ciba Specialty ChemicalsCorp.); Adekastab AO-70 (Asahi Denka Co., Ltd.); Tominox 917 (YoshitomiPharmaceutical Industries, Ltd.); Adekastab AO-80 (Asahi Denka Co.,Ltd.); and Sumilizer GA-80 (Sumitomo Chemical Co., Ltd.).

Specific examples of the sulfur-based antioxidant include dilauryl3,3′-thiodipropionate; dimyristyl 3,3′-thiodipropionate; distearyl3,3′-thiodipropionate; pentaerythritol tetrakis(3-laurylthiopropionate); Sumilizer TPL (Sumitomo Chemical Co., Ltd.); YoshinoxDLTP (Yoshitomi Pharmaceutical Industries, Ltd.); Antiox L (Nippon Oil &Fats Co., Ltd.); Sumilizer TPM (Sumitomo Chemical Co., Ltd.); YoshinoxDMTP (Yoshitomi Pharmaceutical Industries, Ltd.); Antiox M (Nippon Oil &Fats Co., Ltd.); Sumilizer TPS (Sumitomo Chemical Co., Ltd.); YoshinoxDSTP (Yoshitomi Pharmaceutical Industries, Ltd.); Antiox S (Nippon Oil &Fats Co., Ltd.); Adekastab AO-412S (Asahi Denka Co., Ltd.); SEENOX 412S(Shipro Kasei Kaisha, Ltd.); and Sumilizer TDP (Sumitomo Chemical Co.,Ltd.).

Of these, Irganox 1010 (substance name: pentaerythritolyltetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]); Irgaphos 168(substance name: tris(2,4-di-t-butylphenyl) phosphite); Irganox 1076(substance name: octadecyl3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate); Irganox 1330 (substancename:1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene);Irganox 3114 (substance name: tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate); and P-EPQ (substance name: tetrakis(2,4-di-t-butylphenyl)4,4′-biphenylene-di-phosphite) are particularly preferred.

In the present invention, when an antioxidant is employed, the amount ofantioxidant incorporated into the aforementioned propylene polymer resincomposition is 0.001 to 1 parts by mass on the basis of 100 parts bymass of the composition. Addition of an oxidant has, for example, theeffect of preventing yellowing of the composition.

Specific examples of combinations of the aforementioned antioxidants areas follows.

Ex. 1: Irganox 1010 (1,000 ppm)

PEP-Q (1,000 ppm)

Ex. 2: Irganox 1076 (1,200 ppm)

PEP-Q (600 ppm)

Irgaphos 168 (800 ppm)

Ex. 3: Irganox 1010 (400 to 1,000 ppm)

Irgaphos 168 (700 to 1,500 ppm)

Examples of particularly preferred neutralizing agents include calciumstearate, zinc stearate, magnesium stearate, and hydrotalcite (DHT-4A)(compositional formula: Mg_(4.5)Al₂(OH)₁₃CO₃.3.5 H₂O, Li₂Al₄(OH)₁₂CO₃.3H₂O [Mizukal H-1, product of Mizusawa Industrial Chemicals, Ltd.]).

Examples of particularly preferred anti-blocking agents include Sylysia(a synthetic-silica-based agent, product of Fuji Silysia Chemical Ltd.)and Mizukasil (a synthetic-silica-based agent, product of MizusawaIndustrial Chemicals, Ltd.).

Examples of particularly preferred slip agents include erucamide,oleamide, stearamide, behenamide, ethylene bis stearamide, ethylene bisoleamide, stearyl erucamide, and oleyl palmitamide.

Examples of the anti-fog agent include glycerin fatty acid estercompounds such as (di)glycerin mono(di, tri)oleate, (di)glycerinmono(di, tri)stearate, (di)glycerin mono(di)palmitate, and (di)glycerinmono(di)laurate; sorbitan fatty acid ester compounds such as sorbitanlaurate, sorbitan palmitate, sorbitan (tri)stearate, and sorbitan(tri)oleate; ethylene oxide addition products such as polyoxyethylenealkyl(phenyl) ether, polyoxyethylenesorbitan monooleate, andpolyoxyethyleneglycerin monostearate; and propylene glycol fatty acidesters such as propylene glycol monolaurate, propylene glycolmonopalmitate, propylene glycol monostearate, and propylene glycolmonooleate. A plurality of these anti-fog agents may be employed incombination. In the case where a wrap film is formed from the resincomposition containing an anti-fog agent, when a product to be displayedis wrapped with the film, haze of the film caused by generation of vaporfrom the product can be prevented, and transparency of the film can bemaintained, whereby the value of the product can be enhanced.

When a nucleating agent is employed, the amount of a nucleating agentincorporated into the resin composition containing [I] the propylenepolymer and [II] the olefin-based polymer is typically at least 10 ppm,preferably 10 to 10,000 ppm, more preferably 10 to 5,000 ppm, much morepreferably 10 to 2,500 ppm, on the basis of the entirety of thecomposition.

The resin composition for forming the wrap film or shrink film of thepresent invention can be produced by dry-blending a mixture of theaforementioned [I] specific propylene polymer, [II] the olefin-basedpolymer and a predetermined amount of various optional additivesemploying a melt-kneading apparatus such as an extruder or a banburymixer.

The wrap film of the present invention can be formed from the resincomposition pellets produced above through, for example, T-die castmolding, inflation molding, or calender molding. The wrap film isproduced through the following procedure: the resin composition isheated to about 190 to about 270° C., and then subjected to extrusionand cooling. The film may be cooled through air-cooling orwater-cooling.

Even when subjected to no stretching, the wrap film of the presentinvention satisfactorily functions as a wrap film. However, if desired,the wrap film may be subjected to biaxial stretching by means of a knownmethod. Through such stretching, cutting-ability of the wrap film can beimproved. The thickness of the wrap film of the present invention istypically 5 to 40 μm, preferably 10 to 20 μm. The thickness of the wrapfilm is appropriately determined in consideration of, for example, theintended use of the wrap film and the product form thereof.

The shrink film of the present invention can be produced as follows: abase film for stretching is formed from the resin composition pelletsproduced above by means of a known melt-extrusion method; andsubsequently the base film is subjected to stretching in thelongitudinal and lateral directions. Examples of the melt-extrusionmethod that may be employed include T-die cast molding and inflationmolding. Through such a method, a base film for stretching having athickness of 100 to 700 μm, preferably 200 to 500 μm, is formed. Thebase film is produced through the following procedure: the resincomposition is heated to about 190 to about 270° C., and then subjectedto extrusion and cooling. The film may be cooled through air-cooling orwater-cooling.

Subsequently, the base film thus produced is subjected to stretching inthe longitudinal and lateral directions; i.e., biaxial stretching. Thebase film produced through T-die casting molding is subjected to biaxialstretching by means of a tenter process. The base film produced throughinflation molding is subjected to biaxial stretching by means of atubular process. In the course of biaxial stretching by means of atenter process, longitudinal stretching may be carried out simultaneouswith lateral stretching, or longitudinal stretching and lateralstretching may be carried out separately; i.e., multi-stage biaxialstretching may be carried out. The length (or the width) of thethus-stretched film is 1.5 to 20 times, preferably 2 to 17 times, morepreferably 3 to 15 times, the length (or the width) of the base film.Stretching conditions, including heating temperature and stretchingrate, are appropriately determined in consideration of, for example,physical properties of [I] the propylene polymer, physical properties of[II] the olefin-based polymer, the incorporation ratio between thesepolymers, melting characteristics of the resin composition, thethickness of a base film for stretching, and stretching magnification.If desired, after completion of biaxial stretching, the shrink film ofthe present invention may be subjected to heat treatment underappropriate conditions.

Basically, the wrap film or shrink film of the present invention is asingle-layer film formed from the aforementioned resin composition.However, the wrap film or shrink film may be a multi-layer filmcontaining at least one layer formed from the resin composition. Themulti-layer film may be formed from a resin composition in which [I] thespecific propylene polymer employed in the present invention satisfiesthe aforementioned requirements; or a resin composition which differsfrom the aforementioned resin composition in formulation of an additive,wherein [I] the propylene polymer satisfies the aforementionedrequirements and compositional proportion.

The multi-layer film may contain a layer formed from the resincomposition for forming the wrap film or shrink film of the presentinvention, and at least one layer formed from a resin appropriatelyselected from olefin-based resins other than [II] the above-specifiedolefin-based polymer. In such a case, the proportion of the layer formedfrom the resin composition containing [I] the specific propylene polymeris 1 to 99%, preferably 20 to 80%. Preferably, the layer constitutes atleast one outer layer of the multi-layer film, in view that effects ofthe present invention can be obtained. The aforementioned olefin-basedresin may be appropriately selected from the above-specified examples of[II] the olefin-based polymer contained in the aforementioned resincomposition.

The wrap film thus produced of the present invention exhibits excellentsafety, flexibility, wrapping-ability (adhesion), transparency,restoration from deformation, poking resistance, and cutting-ability. Inaddition, since the wrap film does not generate a toxic substance whenincinerated, the film is environmentally friendly. Therefore, the wrapfilm of the present invention is suitable for packaging foods placed onfoaming-resin-made trays for storage in a refrigerator or a freezer, andis suitable for use as a wrap film for commercial or household use.

Meanwhile, the shrink film of the present invention produced aboveexhibits excellent heat shrinking-ability, side welding characteristics,hot slip characteristics, safety, flexibility, shrink-packagingappearance, transparency, and breakage resistance of a product packagedwith the film. In addition, since the shrink film does not generate atoxic substance derived from chlorine when incinerated, the film isenvironmentally friendly. Therefore, the shrink film of the presentinvention is suitable for packaging of an individual food product suchas a cup noodle product, for packaging of a plurality of products suchas yogurt products stored in containers, fruit-processed foods, anddairy foods, for packaging of packs of canned beer, canned juice, etc.,and for heat-shrink packaging of various products such as stationeryitems (e.g., a notebook).

The present invention will next be described in more detail by way ofExamples, which should not be construed as limiting the inventionthereto.

Production of [I] Propylene Polymer (A) Synthesis of a Complex

Synthesis of(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-trimethylsilylmethylindenyl)zirconiumDichloride

In 50 milliliter THF placed in a Schlenk bottle, 3.0 g (6.97 millimole)of a lithium salt of(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(indene) was dissolvedin and the resultant solution was cooled to −78° C. After slowlydropping 2.1 milliliter (14.2 millimole) of Iodomethyltrimethylsilane tothe solution, the resultant mixture was stirred at room temperature for12 hours. The solvent was removed from the mixture by distillation, andsubsequently 50 milliliter of ether was added to the residue, which wassubsequently washed with a saturated ammonium chloride solution. Bydrying an organic phase after phase separation of the residue andremoving the solvent, 3.04 g (5.88 millimole) of(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-trimethylsilylmethylindene)was obtained (yield: 84%).

Subsequently, 3.04 g (5.88 millimole) of the obtained(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-trimethylsilylmethylindene)and 50 milliliter of ether were placed in a Schlenk bottle under anitrogen flow. The resultant solution was cooled to −78° C., and 7.6milliliter (11.7 millimole) of n-BuLi (hexane solution: 1.54 M) wasadded to the solution, which was then stirred at room temperature for 12hours. The solvent was removed from the mixture through distillation,and the solid product was washed with 40 milliliter of hexane, to obtain3.06 g (5.07 millimole) of a lithium salt as an ether addition product(yield: 73%).

The obtained lithium salt was subjected to ¹H-NMR (90 MHz, THF-d₈)measurement. The results are as follows: δ0.04 (s, 18H, trimethylsilyl),0.48 (s, 12H, dimethylsilylene), 1.10 (t, 6H, methyl), 2.59 (s, 4H,methylene), 3.38 (q, 4H, methylene), 6.2-7.7 (m, 8H, Ar—H).

The lithium salt was dissolved in 50 milliliter of toluene under anitrogen flow. The resultant solution was cooled to −78° C., and asuspension of 1.2 g (5.1 millimole) of zirconium tetrachloride in 20milliliter of toluene, which had been cooled to −78° C., was addeddropwise to the solution. After completion of addition, the resultantmixture was stirred at room temperature for six hours. The solvent wasremoved from the resultant reaction mixture through distillation. Theresultant residue was recrystallized from dichloromethane, to obtain 0.9g (1.33 millimole) of (1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-trimethylsilylmethylindenyl)zirconiumdichloride (yield: 26%).

The obtained zirconium dichloride was subjected to ¹H-NMR (90 MHz,CDCl₃) measurement. The results are as follows: δ0.0 (s, 18H,trimethylsilyl), 1.02, 1.12 (s, 12H, dimethylsilylene), 2.51 (dd, 4H,methylene), 7.1-7.6 (m, 8H, Ar—H).

(B) Polymerization of Propylene

A stainless-steel-made autoclave having an agitator and with a capacityof 10 litter was successively received 4 liter of n-heptane, 2 millimoleof triisobutylaluminum, 2 millimole of methyl aluminoxane (availablefrom Albemarle Corp.) and 2 μmole of the foregoing(1,2′-dimethylsilylene)(2,1′-dimethylsilylene)-bis(3-trimethylsilylmethylindenyl)zirconiumdichloride. After introducing hydrogen into the autoclave until theinterior pressure reached 0.06 MPa (gauge), and while elevating thetemperature of the autoclave to 60° C., propylene gas was introducedinto the autoclave until the interior pressure reached 0.8 MPa (gauge),to thereby allow polymerization to proceed. During polymerization,propylene gas was continuously introduced into the autoclave by the useof a pressure-regulating apparatus, so as to maintain the interiorpressure at 0.8 MPa (gauge). After polymerization was performed at 60°C. for 30 minutes, the resultant product was removed from the autoclave,and the product was dried under reduced pressure, to obtain [I] thepropylene polymer.

(C) Evaluation of Propylene Polymer

(i) Measurement of a Pentad Fraction

A pentad fraction was measured by means of the above-described method inthe description.

(ii) Measurement of an Intrinsic Viscosity [η]

An intrinsic viscosity [η] of the polymer was measured at 135° C. intetralin using an automatic viscometer (model: VMR-053, produced by ofRigosha Co., Ltd.)

(iii) Determination of an Amount of a Component That is Eluted at 25° C.or Lower Through Temperature Rise Chromatography

The amount of a component which is not adsorbed onto a filler containedin a TREF column and is eluted from the column (column temperature: 25°C.); i.e., W25 (mass %), was obtained on the basis of an elution curvethrough the following procedure.

(a) Operation Method

A sample solution was introduced into a TREF column whose temperaturewas regulated to 135° C., and subsequently the temperature of the columnwas gradually lowered to 0° C. with a cooling rate of 5° C./hour, andthe temperature of the column was maintained at 0° C. for 30 minutes, sothat the sample was adsorbed onto a filler. Thereafter, the column washeated to 135° C. with a rising rate of 40° C./hour, and an elutioncurve was obtained.

(b) Apparatus

TREF column: Silica gel column (4.6φ×150 mm) (produced by GL SciencesCompany)

Flow cell: KBr cell (optical path length: 1 mm) (produced by GL SciencesCompany)

Liquid feeding pump: SSC-3100 pump (produced by Senshu Science Co.,Ltd.)

Valve oven: MODEL554 oven (high temperature type) (produced by GLSciences Company)

TREF oven: Product of GL Sciences Company

Dual system temperature controller: REX-C100 temperature controller(produced by Rigaku Kogyo Company)

Detector: Infrared detector for liquid chromatography (MIRAN 1A CVF,produced by of FOXBORO Company

10-way valve: Electric valve (produced by Barco Company)

Loop: 500-μliter loop (produced by Barco Company)

(c) Measurement Conditions

Solvent: o-dichlorobenzene

Sample concentration: 7.5 g/litter

Injection amount: 500 μlitter

Pumping flow rate: 2.0 milliliter/minute

Detection wave number: 3.41 μm

Column filler: Chromosorb P (30 to 60 mesh)

Column temperature distribution: within ±0.2° C.

(iv) Measurement of a Molecular Weight Distribution (Mw/Mn)

A Mw/Mn was measured using the following apparatus under the followingcondition.

GPC apparatus: WATERS 150C

Column: TOSO GMHHR-H(S)HT

Detector: RI detector for liquid chromatography

Solvent: 1,2,4-trichlorobenzene

Measurement temperature: 145° C.

Flow velocity: 1.0 milliliter/minute

Sample concentration: 2.2 mg/milliliter

Injection amount: 160 μlitter

Calibration curve: Universal Calibration

Analytic program: HT-GPC (Ver. 1.0)

(v) DSC Measurement

A differential scanning calorimeter (DSC-7, produced by Perkin ElmerCo., Ltd.) was used. After melting 10-mg sample by heating at 220° C.for three minutes in a nitrogen atmosphere, the melted sample was cooledto −40° C. at a cooling rate of 1° C./minute and a crystallizationexothermic curve was prepared. The temperature corresponding to the topof the maximum peak of the exothermic curve was defined as acrystallization temperature (Tc). The sample was maintained at −40° C.for three minutes, and then heated at a temperature rising rate of 10°C./minute, to obtain a melting endothermic amount expressed as (ΔH). Thetemperature corresponding to the top of the maximum peak of the obtainedmelting endothermic curve was defined as a melting point (Tm).

(D) Physical Properties of [I] Propylene Polymer

(1) Meso pentad fraction (mmmm): 0.45

(2) [rrrr/(1−mmmm)]: 0.044 [rrrr: 0.024]

(3) Intrinsic viscosity [η]: 1.5 decilitter/g

(4) Amount of a component which is eluted at 25° C. or lower throughtemperature-programmed chromatography (W25): 91 mass %

(5) Molecular weight distribution (Mw/Mn): 2.0

(6) Melting point: 81° C.

(7) Melting endotherm (ΔH): 25 J/g

(8) Melt flow rate (MFR: 230° C., load: 21.18 N): 6 g/10 minutes

EXAMPLES 1 TO 4 (A) Production of Pellets

A phenol-based antioxidant (Irganox 1010) (500 ppm) and aphosphorus-based antioxidant (Irgaphos 168) (1,000 ppm) were added to[I] the propylene polymer produced above, and the resultant mixture wassubjected to extrusion at a resin temperature of 200° C. by the use of asingle screw extruder (model: TLC35-20, product of Tsukada JukiSeisakusho Co., Ltd.), to obtain pellets.

(B) Production of Wrap Film

The pellets produced in (A), IDEMITSU PP F-704NP (melt flow rate: 7 g/10minutes) and IDEMITSU PP F-734NP (melt flow rate: 6 g/10 minutes) (bothavailable from Idemitsu Petrochemical Co., Ltd.) were dry-blended atcompositional proportions shown in Table 1. Subsequently, a wrap film(thickness: 20 μm) was formed from the resultant mixture by the use of aVS 40-mm extruder and a T-die casting apparatus (produced by TanabePlastic Kikai Co., Ltd.) under the following film formation conditions.

Temperature of the resin at a die outlet: 230° C.

Chill roll temperature: 30° C.

Drawing rate: 18 m/minute

(C) Evaluation of Wrap Film

The obtained wrap film was subjected to conditioning at a temperature of23° C.±2° C. and a humidity of 50±10% for 16 hours or more, and the wrapfilm was evaluated in terms of the following items at the abovetemperature and humidity. The evaluation results are shown in Table 1.

(i) Transparency (Haze)

Transparency was Measured in Accordance With JIS K7105.

(ii) Tensile Yield Strength and Tensile Elastic Modulus

Tensile yield strength and tensile elastic modulus were measured througha tensile test in accordance with JIS K7127.

Crosshead speed: 50 mm/minute

Measurement direction: machine direction (MD direction)

(iii) Wrapping-ability 1

The opening of a stainless-steel-made vat (inner dimensions: 125×180 mm,depth: 70 mm) was wrapped with a cut wrap film (160×220 mm). The wrappedvat was allowed to stand at 5° C. for one week. When removal of the filmdid not occur and wrapping was maintained, rating “A” was assigned,whereas when removal of the film occurred and wrapping was notmaintained, rating “C” was assigned.

(iv) Wrapping-ability 2

A cut wrap film (160×170 mm) was placed on the opening of theaforementioned vat such that a first shorter side edge of the film was30 mm or 50 mm inward from a first shorter side of the vat, and a secondshorter side edge of the film was caused to adhere to a second shorterside of the vat. Subsequently, the film was gradually stretched bypinching the center portion of the first shorter side edge, to therebycover the entire opening of the vat. When the entire opening of the vatcould be covered with the film in two cases where the first shorter sideedge of the film was 30 mm inward, and 50 mm inward, from the firstshorter side of the vat, rating “A” was assigned; when the entireopening of the vat could be covered with the film merely in the casewhere the first shorter side edge of the film was 30 mm inward from thefirst shorter side of the vat, rating “B” was assigned; and when theentire opening of the vat could not be covered with the film in the casewhere the first shorter side edge of the film was 30 mm or 50 mm inwardfrom the first shorter side of the vat, rating “C” was assigned.

(v) Poking Resistance

The opening of the aforementioned vat was wrapped with a wrap film in amanner similar to the case where wrapping-ability 1 was evaluated, andsubsequently the center portion of the film was slowly poked with afinger. When the film was not broken until the center portion of thefilm reached the bottom of the vat, rating “A” was assigned, and whenthe film was broken before the center portion of the film reached thebottom of the vat, rating “C” was assigned.

(vi) Restoration From Deformation (Elasticity)

A dice (size of each side: 45 mm) was placed on the center of the bottomof the aforementioned vat, and the vat was wrapped with a wrap film in amanner similar to the case where wrapping-ability 1 was evaluated.Subsequently, the center portion of the film was slowly poked with afinger. When the center portion of the film reached the dice placed onthe bottom of the vat, the finger was removed from the film. The stateof the film was observed three minutes after removal of the finger. Whenthe film was restored to the original state, rating “A” was assigned;when a pouch-like mark remained in the film, rating “B” was assigned;and when the film was broken, rating “C” was assigned.

COMPARATIVE EXAMPLE 1

A commercially available polyvinylidene-chloride-made wrap film [tradename: Saran Wrap R, available from Asahi Chemical Industry Co., Ltd.]was evaluated in a manner similar to that of Example 1. The results areshown in Table 1.

TABLE 1 Compositional Comp. proportions (mass %) Ex. 1 Ex. 2 Ex. 3 Ex. 4Ex. 1 [I] Propylene polymer 70 70 90 50 — [II] Olefin-based polymerF-704NP 30 — 10 50 — F-734NP — 30 — — — Evaluation of wrap film Haze (%)0.3 0.3 0.5 0.6 0.3 Tensile elastic modulus 130 130 70 270 1250 (MPa)Tensile yield strength 8.3 8.0 6.4 11.4 No (MPa) yield pointWrapping-ability 1 A A A A A Wrapping-ability 2 A A A B C Pokingresistance A A A A C Restoration from A A A A C deformation In Table 1,“Ex.” and “Comp.” are abbreviations of “Example” and “Comparative”respectively.

EXAMPLES 5 TO 8, COMPARATIVE EXAMPLES 2 AND 3 (A) Production of Pellets

A phenol-based antioxidant (Irganox 1010, available from Ciba SpecialtyChemicals COrp.) (1,000 ppm) and a phosphorus-based antioxidant (P-EPQ,available from Ciba Specialty Chemicals Corp.) (500 ppm) were added to[I] the propylene polymer produced above, and the resultant mixture wassubjected to extrusion at a resin temperature of 200° C. by the use of asingle screw extruder (model: TLC35-20, produced by Tsukada JukiSeisakusho Co., Ltd.), to obtain pellets.

(B) Production of Base Film

The pellets produced in (A), IDEMITSU PP F-300S (melt flow rate: 3 g/10minutes, available from Idemitsu Petrochemical Co., Ltd.), and apropylene-based random copolymer described in Example 1 of JapanesePatent Application Laid-Open (kokai) No. 10-152531 (R-PP, melt flowrate: 2.3 g/10 minutes, ethylene content: 4.2 mass %, melting point:137.2° C.) were dry-blended at compositional proportions [mass %] shownin Table 2. Subsequently, a tubular, base film (thickness: 240 μm) wasproduced from the resultant mixture by the use of a single three-layerbottom-blowing water-cooling film formation apparatus including three40-mmφ extruders and a 50-mmφ circular die, at a die outlet temperatureof 230° C.

(C) Production of Stretched Shrink Film

The base film produced in (B) was subjected to biaxial stretching at astretching temperature of 100 to 120° C. and stretching magnifications(longitudinal: ×6, lateral: ×5) by use of a tubular-type biaxialstretching film formation apparatus including upper and lower niprollers and a heating furnace provided between the nip rollers, theheating furnace including a preliminary heating apparatus and a heatingapparatus, to thereby produce a stretched film. Subsequently, thestretched film was subjected to heat treatment at 70° C. for 10 secondsby use of the aforementioned stretching apparatus, to thereby produce ashrink film (thickness: 12 μm). The shrink film was evaluated by meansof the methods described below. The evaluation results are shown inTable 2.

(D) Evaluation of Shrink Film

The shrink film was subjected to conditioning at a temperature of 23°C.±2° C. and a humidity of 50±10% for 16 hours or more, and the shrinkfilm was evaluated in terms of the following items at the abovetemperature and humidity. The evaluation results are shown in Table 2.

(i) Transparency (Haze)

Transparency was measured in accordance with JIS K7105.

(ii) Shrink Packaging Appearance

A commercially available instant noodles (stir-fried Chinese noodles)product having a rectangular parallelepiped shape was loosely packagedwith the foregoing shrink film, and the edges of the film were bondedtogether through side welding. The packaged product was placed on aconveyer, and caused to pass through a hot-air-circulation-type heatingfurnace (model: NS-350, produced by of Kyowa Electric Co., Ltd.), tocause shrinkage of the film. After heat shrinkage, the size of cornerflange and the amount of wrinkles generated on a corner portion werevisually evaluated.

(iii) Hot Slip Characteristics

Hot slip characteristics were evaluated on the basis of occurrence ofblocking when a plurality of the foregoing shrink-packaged instantnoodle products were caused to adhere to one another at the outlet ofthe heating furnace, and ease of passage of the adhered products throughthe conveyer.

(iv) Heat Shrinkage Stress

The procedure of (ii) above was repeated, except that a commerciallyavailable instant noodle product was somewhat tightly packaged with theforegoing shrink film, to thereby obtain a shrink-packaged product, andthe product was subjected to visual evaluation. When deformation of theproduct was not observed, rating “A” was assigned, whereas whendeformation of the product was observed, rating “C” was assigned.

In Comparative Example 2, a shrink film was formed solely from IDEMITSUPP F-300S (available from Idemitsu Petrochemical Co., Ltd.) serving as apolypropylene resin. In Comparative Example 3, a shrink film was formedsolely from R-PP, which was employed in Examples 7 and 8.

TABLE 2 Compositional proportions (mass %) Comp. Comp. Ex. 5 Ex. 6 Ex. 7Ex. 8 Ex. 2 Ex. 3 [I] Propylene polymer 70 50 70 50 — — [II]Olefin-based F-300S 30 50 — — 100 — polymer R-PP — — 30 50 — 100Evaluation of Haze 0.2 0.2 0.4 0.5 0.5 2.0 shrink film (%) Glossiness154 153 148 145 146 127 (%) Shrink Good Good Good Good Poor Goodpackaging appearance Hot slip Good Good Good Good Good Goodcharacteristics Heat shrinkage A A A A C C stress

In Table 2, “Ex.” and “Comp.” are abbreviations of “Example” and“Comparative” respectively.

Industrial Applicability

The wrap film of the present invention does not generate a toxic gasderived from chlorine, such as hydrogen chloride gas or dioxin, whenincinerated; is environmentally friendly; and exhibits safety andtransparency comparable to those of a widely used wrap film formed froma polyvinylidene chloride resin. In addition, the wrap film of thepresent invention is superior to the polyvinylidene-chloride-made wrapfilm in terms of poking resistance and restoration from deformation.

Since the shrink film of the present invention contains no chlorine, theshrink film does not generate a toxic gas derived from chlorine, such ashydrogen chloride gas or dioxin, when incinerated. Since the shrink filmcontains no plasticizer, when the film is employed, problems caused byelution of a plasticizer do not arise. Therefore, the shrink filmexhibits safety and is environmentally friendly. In addition, the shrinkfilm is excellent in terms of heat shrinking-ability during packaging,low-temperature shrinking-ability, melting-breakage resistance, sidewelding characteristics, hot slip characteristics, and appearance afterpackaging (i.e., the edge of the film adheres to an object withoutforming wrinkles). Furthermore, the shrink film of the present inventionexhibits considerably excellent transparency and glossinessiness ascompared with a conventional polyolefin-based resin shrink film, andenables production of a shrink-packaged product of high value.Therefore, the shrink film of the present invention is envisaged to beemployed in a variety of fields.

What is claimed is:
 1. A wrap film formed from a resin composition comprising [I] a propylene polymer in an amount of 1 to 99 mass %, and [II] an olefin-based polymer in an amount of 99 to 1 mass %, wherein [I] the propylene polymer satisfies the following requirements of: (1) a meso pentad fraction (mmmm) is 0.2 to 0.6, and (2) a racemic pentad fraction (rrrr) and (1−mmmm) satisfy the following relation: [rrrr/(1−mmmm)]≦0.1.
 2. The wrap film according to claim 1, wherein said [I] propylene polymer satisfies the following requirement of: (3) an intrinsic viscosity [η] measured at 135° C. in tetralin is 1 to 3 deciliter/g.
 3. The wrap film according to claim 1, wherein said [I] propylene polymer satisfies the following requirement of: (4) an amount of a component which is eluted at 25° C. or lower through temperature-programmed chromatography (W25) is 20 to 100 mass %.
 4. The wrap film according to claim 1, wherein said [I] propylene polymer is polymerized by the use of a metallocene catalyst containing a promoter and a transition metallic compound in which a cross-linking structure is formed via two cross-linking groups.
 5. The wrap film according to claim 1, wherein said [II] olefin-based polymer is a propylene-based polymer.
 6. A multi-layer wrap film comprising at least one layer formed from a resin composition as recited in claim
 1. 7. A stretched shrink film formed from a resin composition comprising [I] a propylene polymer in an amount of 1 to 99 mass %, and [II] an olefin-based polymer in an amount of 99 to 1 mass %, wherein [I] the propylene polymer satisfies the following requirements of: (1) a meso pentad fraction (mmmm) is 0.2 to 0.6, and (2) a racemic pentad fraction (rrrr) and (1−mmmm) satisfy the following relation: [rrrr/(1−mmmm)]≦0.1.
 8. The shrink film according to claim 7, wherein said [I] propylene polymer satisfies the following requirement of: (3) an intrinsic viscosity [η] measured at 135° C. in tetralin is 1 to 3 deciliter/g.
 9. The shrink film according to claim 7, wherein said [I] propylene polymer satisfies the following requirement of: (4) an amount of a component which is eluted at 25° C. or lower through temperature rise chromatography (W25) is 20 to 100 mass %.
 10. The shrink film according to claim 7, wherein said [I] propylene polymer is polymerized by the use of a metallocene catalyst containing a promoter and a transition metallic compound in which a cross-linking structure is formed via two cross-linking groups.
 11. A shrink film according to claim 7, wherein said [II] olefin-based polymer is a propylene-based polymer.
 12. A multi-layer shrink film comprising at least one layer formed from a resin composition as recited in claim
 7. 